1. Technical Field
This disclosure relates generally to digital imaging calibration, and, more specifically, to calibration of rotational offset in digital imaging.
2. Description of the Related Art
Device sensors, for example, camera sensors on portable devices, are allowed certain tolerances, both during manufacture of the sensor and as part of incorporation of the sensor into a device. Ideally, a camera sensor will be aligned with the body of the device such that the axes of the photo array or pixels are aligned with the axes of the device as well as the axes of an orientation sensor of the device. However, due to manufacturing tolerances, the ideal alignment requires expensive components and challenging manufacturing. Various features of the manufacturing process, for example, tolerances related to mounting of the camera module in the device, or mounting of the image sensor die in the camera module mean that the camera is often rotationally misaligned with the device. Such misalignment may cause the captured image to be rotated from a desired alignment.
Camera orientation within a device can be calibrated during manufacturing. For example, the rotational misalignment of the image sensor die with respect to the device casing or the gravity vector of the orientation sensor in the device can be measured and used for calibration as part of the manufacturing process, but such calibration increases the manufacturing time and cost. Such methods of camera sensor alignment require significant investment of resources (e.g., materials and time) by the manufacturer. Additionally, accurate alignment during manufacture cannot possibly account for changes over time (e.g., due to drops) and as such, an initial alignment or calibration may become obsolete.